12/12 from seed

Im looking into doing a 12 12 from seed grow and was wondering what I need to know before i start. Im under a 400w mh in a spare bathroom in my basement with nectar for the gods nutes simple line

I don't know why anyone would go for 12/12 from seedling unless the want REALLY small plants. Give them at least a couple of weeks at 24, you will be much better off.

most common reason for 12/12 from seed is limit on lights and rooms. 1 light 1 room = 1 cycle

I believe if you are going with a sativa or heavy sativa dom you could be ok, but with indica you will have a very small plant. You don't give a height that your space can handle, so I realize much could be dependent on that. Usually you will be much happier if you can give the seedlings a couple to 4 weeks vegs. Best of luck.